I think I understand now.
If you imported a few users, they should be given the option via UI to have the verification email sent to them again (if you are using the OAuth flows/hosted pages)
If you are not using the OAuth flows in Fusionauth (this seems to be true, based on what you said), then I think that you would need to offer the user the ability to now verify through this API
https://fusionauth.io/docs/v1/tech/apis/users/#resend-verification-email, which will return a verificationId
Also, there is a tutorial for email verification (the gating part is a paid feature) and we are developing one (very similar) for application registrations as well (the gating part is a paid feature).
https://fusionauth.io/docs/v1/tech/tutorials/gate-accounts-until-verified/
Let me know if that more gets at your question.
Thanks,
Josh