I have a 2007 Chevy Impala 3.5l v6. squealing/scratching noises in the belt pulleys area. Is it one of the pulleys?

Is the new belt the correct size and is it squealing too? Then it's possible the pulley bolt (that holds the pulley on) may have woked loose a bit. If you can't exactly tell where the noise is coming from here's how you can usually tell: Take a 1 or two foot length of 1/2" or so rubber hose, put one end in your ear and VERY carefully put the other end of the hose NEAR (not on) the different pulleys and components down there. Also, be very careful to not have your hands or fingers anywhere near any miving parts. The hose will amplify the noises and you can usually tell where different noises are coming from this way. Another thing you can try...... Spray a quick small spray of WD 40 (or any spray like that) on the suspect pulley. If it stops squeaking, there's the culprit.

Yes the belt is the correct size I compared the new and the old Bc I thought it was too small Bc I couldn't get it on the alternator pulley when I moved the tensioner but I had it on wrong lol. But anyways, would it be possible it could be the tensioner pulley or the idler pulley?

If the noise persists after putting on the new belt and cleaning the pulleys, it may be a bearing. I'd guess first it will be the water pump as they go out more often that others. Using he hose is a great way. There also is a spray to put on the belt / pulleys when you run it to clean it and ad tackiness to the system. Does the noise only start when you first fire it up or continue on a constant pace? If it is constant, I'd be thinking a pulley bearing.