Hello. Can I continue to use imagery downloaded during the free trial after cancelling membership?
Yes, you're free to use licensed items according to the licensing terms, even after cancelling your (free trial) subscription. Credits still in your account will, however, vanish. You need to license the assets you want to use.
Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based on reading and interpreting the licence terms and on fair use for both the buyer and the artist/stock company, but I cannot rule out that my interpretation is wrong. I'm not an Adobe employee).