Can i exhaust Deceiver leblanc to make a copy relfection of a reflection token unit which conquered ?

Yes — a Reflection token is a unit, so it's a legal "another unit there" for Deceiver's reflexive copy trigger (FAQ #12626). Pay the trigger cost (discard 1, exhaust Deceiver) when you conquer or hold, play the ready Reflection token there, then the reflexive trigger copies the existing Reflection.

The wrinkle: copy effects only see copyable traits, so your new token becomes a copy of whatever card the original Reflection is copying — printed name, Might, rules text (Rule 479.1.b, "copy copy copy"). The Temporary on the new token comes from Deceiver's own text, not from the target, so it gets it no matter what it copies.

Timing note: the copy target is chosen when the reflexive trigger finalizes, so if the Reflection you intend to copy leaves that battlefield before resolution (bounced or moved to Base), the copy fails and you're left with a 0 [M] Reflection that still has Temporary (FAQ #12985).