Open the exact GA4 account you want to connect to Make.com and go to the Admin section of your account. Under Property look for your property ID. Copy that.
Add a new GA4 module to your Make.com scenario and just past your property ID. After you click Save a popup will appear asking you to login to your Google account (make sure it's the one linked to your GA4 property). After a couple of seconds the connection will be verified.