I can't find my bottom metal retainers. is it okay if i use my clear whitening molds as retainers?

Not the same: Using your "whitening mold" as retainers is a good temporary fix. They are better than wearing nothing at all, however, they will not hold your teeth in proper position long term as they are made from more flexible material and have reserve spaces to hold the whitening gel. To keep your teeth from drifting out if position have your orthodontist made you a new set of retainers.

Temporarily: Until you can see your Orthodontist or treating General Dentist. Trays and retainers are made from different materials, fit differently, and are designed to do different tasks. Best thing is to return to the practitioner that did your Orthodontic treatment for review and recommendation.