How do I create search for multiple fields in dataset?

Ok, we have some ERRORs here. You are not doing exactly what a suggest you.

Try this one…

import wixData from"wix-data";

$w.onReady(function(){   }

export function dropdown1_change(event) {xxx()}

function xxx() {
    wixData.query("therapies")    
    .contains('therapy', $w('#dropdown1').value)    
    .or(wixData.query("therapies")
    .contains('therapyType2', $w('#dropdown1').value))    
    .or(wixData.query("therapies")
    .contains('therapyType3', $w('#dropdown1').value))
    .find()
    .then( (results) => {
        console.log(results)
        $w('#repeater1').data = results.items;
    });
}