Go to Dashboard > Marketing and Seo > Marketing Tools > Tracking Codes.
Do not run a direct GA4 measurement ID and a GTM container at the same time. This causes your purchase event to fire twice, inflating your order and revenue numbers in GA4 and distorting Google Ads bidding if linked. Manage GA4 through GTM only, rather than both.
Your store fires a standard eCommerce data layer on every completed order, so any tag management system can pick up order details automatically without custom code.