WooCommerce Memberships

We have members with a membership number printed on their membership card for over 40 years. So that number is very important. If we lose that people are getting confused.
I have a couple of users on the site (not all of them are members)

I’m currently busy with adding these members to the site for a subscription linked to a membership (CSV, nobody is added to the site yet, hence this question).
But I’m starting to think I better import them first as member with a membership plan according to their subscription and with the membership nummer they have for over 40 years. Next add the subscription to the members plans.

I hope i explained myself well, not easy to tell this sort of stuff in a foreign language 🙂