Neither sounds formal.  A problem that English learners have is that they use some formal verb when there is a common phrasal verb.  If you don't use "to plug in,"  you would have to say something like "please energize the tv" or "please insert the plug of the tv into the electrical outlet."  Thank God for phrasal verbs.

Just remember that you can't use an object pronoun  outside of a separable phrasal verb. (No him, her, it, me, them, us, you.)

I pick up my friend.

I pick my friend up.

I pick him up.

But...

I pick up him. = BAD!