"card_" is the older version of Stripe
"pm_" is the newer version. This will appear when you use Stripe SCA as the payment gateway on the Merchant Facility.
You may have a mixture of the two because you changed the Payment Gateway on the Merchant Facility from "Stripe" to "Stripe SCA" or perhaps the Billing Tokens were migrated from a previous system.
Generally, either can be used and both will work fine, but if you have ones beginning with "pm_" then we recommend using "Stripe SCA". This is nothing to be concerned about.