Baiers solution

scryfall.js

let carddata = [{ scryfallid: '7f3423d7-cb81-47bf-b9a6-a279ba6cedf4' }]
let exportData = [{ scryfallid: 'be8ec9e1-2c8e-496d-9111-4d453b75b578', artnrmagicmonk: '15220000-war-099-en' },{ scryfallid: '7f3423d7-cb81-47bf-b9a6-a279ba6cedf4', artnrmagicmonk: '12345688-war-099-en' }]

let artNrMagicMonk = []

for (let card of carddata) {
    let exp = exportData.find(el => el.scryfallid === card.scryfallid )
    if (exp) {
        artNrMagicMonk.push(exp.artnrmagicmonk)
    }
}