I need help. Is this part of the main quest or is this a side quest thing I can't remember!? Also dragon rend shout for grounding dragons is that apart of the blades missions?

Dragon's Rend is part of the main quest, not connected to the Blades.

About the other part of your question, if you mean trapping a dragon there, yes that is also the main quest.

Numinex is not tied to the Main Quest except as a Wall Decoration. Dragonsreach was built to ensure Numinex was held captive by High King Olaf.

I think OP was asking about the quest involving Odahviing.

(hard to tell exactly what was being asked though.)