Question about op8 stuff plz help

So I have my thing turned on to op8 and I’m turning this quest in to get an op8 sandhawk but it’s only giving me a lvl 72 one how do I get it for op8

Did you accept the mission while you were 72? If so, there is your answer.

If you want a piece of gear at a specific level, you need to accept said mission when you are at the desired level.
At this point, you will either have to reset your playthrough to accept that mission again at op8, or find someone who is willing to trade/give you one.

Ty I think that was my problem but how do I resets my play through

When you load your character you can reset UVHM by going over it (but not selecting it just yet) and pressing the appropriate button. It’s Triangle on the PS3/4, Y on the 360/One and some other key on the PC, don’t know which one.
The game does show you which button to press on the bottom of the box with the difficulties anyway.

Ty for the help