Several concerns

[CODE-NINJA]

Ok, i did some few UPGRADES on my provided code…
See changes here…

import wixData from 'wix-data';
//-------------------USER-INTERFACE------------------------
const DATABASE = "CARS"; //<-- Paste in here the ID of your DATABASE!
const DB_FIELD1 = "model";      //<-- Paste in here the ID of the Database-Field-1!
const DB_FIELD2 = "type";   //<-- Paste in here the ID of the Database-Field-2!
const ddn1 = "#ddnModel";       //<-- Here the ID of your Dropdown-1.
const ddn2 = "#ddnType";        //<-- Here the ID of your Dropdown-2.
//-------------------USER-INTERFACE------------------------
$w.onReady(async()=>{console.log("Page is ready...");
    let itemData = await get_ItemData1(); 
    console.log("Item-Data: ", itemData);
    create_UniqueDropdown(itemData, DB_FIELD1, ddn1);
    $w(ddn1).onChange(async()=>{
        let value = String($w(ddn1).value);
        let itemData = await get_ItemData2(value); 
        create_UniqueDropdown(itemData, DB_FIELD2, ddn2); 
        console.log("xxx", itemData);
    }); 
    $w(ddn2).onChange(async()=>{
        let items = await startSearchEngine();
        console.log("HURAY --> !!! " + items);
    }); 
});

function get_ItemData1() {
    let query = wixData.query(DATABASE)
    query.limit(1000)
    return query.find()
    .then((res)=> {console.log(res);
        console.log(res.totalCount)
        if (res.totalCount>0) {
            let itemData = res.items; 
            return itemData;
        }
        else {console.log("No DB-Entries found!");}
    }).catch((err)=>{console.log(err);});
}

function get_ItemData2(value) {
    return  wixData.query(DATABASE)
    .limit(1000)
    .eq(DB_FIELD1, value)
    .find()
    .then((res)=> {console.log(res);
        console.log(res.totalCount)
        if (res.totalCount>0) {
            let itemData = res.items; 
            return itemData;
        }
        else {console.log("No DB-Entries found!");}
    }).catch((err)=>{console.log(err);});
}
function create_UniqueDropdown(items, dbfield, dropdown) { 
    const uniqueTitles = getUniqueTitles(items); 
    $w(dropdown).options = buildOptions(uniqueTitles); 
    function getUniqueTitles(items) {
        const titlesOnly = items.map(item => item[dbfield]); 
        return [...new Set(titlesOnly)];
    }
    function buildOptions(uniqueList) {
        return uniqueList.map(curr => {
            return {
                label:curr, value:curr
            };
        });
    }
}
function startSearchEngine() {
    wixData.query(DATABASE)
    .limit(1000)
    .contains('departement', String($w(ddn1).value))
    .eq("region", String($w(ddn2).value))
    .ascending("_random")
    .find()
    .then((res)=>{console.log("My found RESULTS: ", res);
        if (res.totalCount>0) {let items = res.items;
            console.log("Items: ", items);
            return items;
        }
        else {console.log("No RESULTS found!!!");}
    })
    .catch((err)=>{console.log("We have a problem ! ---> " + err);});
}

This CODE has been tested now and is working well.

You can find here a little example…

https://russian-dima.wixsite.com/my-site-4/conditional-dropdowns

Here a SCREENSHOT of the used DATABASE…

Some CONSOLE-LOGS…for better understandings and proovement for the correct working of the code.

USED-SETUP:

//------------------------USER-INTERFACE------------------
const DATABASE = "CARS"; //<-- Paste in here the ID of your DATABASE!
const DB_FIELD1 = "model";      //<-- Paste in here the ID of the Database-Field-1!
const DB_FIELD2 = "type";   //<-- Paste in here the ID of the Database-Field-2!
const ddn1 = "#ddnModel";       //<-- Here the ID of your Dropdown-1.
const ddn2 = "#ddnType";        //<-- Here the ID of your Dropdown-2.
//------------------------USER-INTERFACE-------------------

Result inside dropdowns…