Plumbing problem - vanity is taller than the j-drain. How do I lower the j-drain without extensive work?

This is a bath vanity sink with a pop up type stopper right?

Show pic of drain under sink if you can.

Put the trap arm into the wall connection. Measure the distance from the tailpiece or extension to the p trap connection. Then get an extension to fit.

Are you referring to where the horizontal pipe enters the wall?

Yep, Im confused. Please clarify what the problem is. Pics would certainly help. You say the vanity is taller than the P-trap (thats what its called for future reference) but you say you need to lower the p-trap. That's conflicting info. Lets see some pics so we can get you all set up.