WooCommerce: which hook to use to change the expiration of a membership during the first purchase?

Question

In a project, I'm working on using WooCommerce with membership and subscription plugins.

I need to change the date of both the subscription and membership end at the end of the first order.

Using the woocommerce_order_status_completed hook I can run everything by changing the order status from the admin panel, but in runtime probably will be executed before to membership hook because, in the debugging tests I did, I do not find the correlation between subscription and membership in the DB:

SELECT * FROM wp_postmeta WHERE meta_key = '_subscription_id' AND meta_value = 915

but return null.

so....anyone can say what is or where I can found the hook that runs after the link between subscription and membership.

P.S. I also tested the woocommerce_thankyou hook having the same result