Cross Domain Conversion Tracking - From Personal Site to Shopify Store Site

I’m hoping someone in here has run into a similar situation. How do I setup AdWords “conversion tracking” to work when I drive AdWords traffic to my main website i.e. “main site.com” and then have the customer use my Shopify site to complete the purchase checkout process using my Shopify store i.e. “store.shopify.com”?

I can show the purchase conversion coming through to the GA4 account, but I can’t tell if the purchase comes from the AdWords Ads, Organically, etc

Appreciate the help!!