Can i tracking in app purchases?

Unfortunately Search Ads does not track in-app purchase conversions.

The solution that I think would work would be to follow the instructions here: https://searchads.apple.com/advanced/help/measure-results/#attribution-api to firstly track if a user has installed the app through Search Ads. Then what you can do is store this in a table in Firebase for example. This would be your first column and would say whether the app download originated from Search Ads. Then, in a second column (In-App Purchase Made), when a user makes an in-app purchase, you could update this to show "True" and then using that information you'd be able to see in a table which of your users originated from Search Ads and then which of those went on to buy an in-app purchase.

Obviously this isn't an official method and does take a bit of work but if it is a requirement, I see this as the only solution. Shame Apple doesn't support it officially.

Thanks for this tip!!