@PATGRNY, Welcome to HP Support Community!
I see that you have cartridges from your old printer and would like to know what to do next, well I shall help you with it.
Firstly, you paid for the pages printed and not cartridges while the OJ 8620 printer was enrolled in HP Instant Ink Program. The cartridges cannot be used on any other printer, the only option is to send it back to HP in the return envelope you have.
I hope that answers your concern adequately. Let me know!
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TEJ1602
I am an HP Employee