# Confusion in trying to apply Newton's 3rd law to friction

I have tried to answer this question through searching on this website, since I realise similar questions have already been asked, but I didn't manage to find a definite and clear answer to the following.

Say you pushed a block to the right over a plank that was lying on a frictionless surface. The block exerts an equal force on you (say, 5N) as you are exerting on the block (also 5N). The force of friction on the block by the plank (say, 3N) is to the left, opposite to the direction of motion of the block. Some of the threads I read seemed to be suggesting that the partner force to the force of friction on the block by the plank was a force of friction on the plank by the block, in which case this partner force should be to the right, in the opposite direction to the 1st force of friction. Now, would the plank then move to the left or the right? I'm so confused, because I know that the direction of the friction is supposed to be opposite to the direction of the motion of an object, so if the force of friction on the plank by the block is to the right, then that must be because the plank is moving to the left. But if you reason it another way, then the plank should move to the right because there are no forces acting on it except this 3N of friction exerted by the block, and a force causes an acceleration. So which way would it move, and why?

Also, I feel like I don't have much intuition for this concept of there being two frictional forces between the block and the plank, one to the left and one to the right (if I am right that this is what Newton's law implies). I can't really imagine it, because I have only ever thought about friction as arising to oppose the motion of one object, so I would really appreciate it if anyone could help me picture this better.