100amp Sub panel next to the main 200 amp panel

[mylk100]

I am removing a 60 amp sub panel and installing a 125 amp main lug only panel. I have to change out the wires, the panel and the breaker feeding the sub to 100amps.
Mind you, I have material that I'm using from the scrap. I have a 3 individual #2 al or 3 individual #3 cu that I can use. The main sits in a garage on a wall and the sub is directly next to it. Could I use any of these wires to wire a 100 amp or do I need to go higher? I understand I also need a ground. What is the smallest ground needed? I do have left over #8 cu so I'm hoping to use that up. Thanks for everyone chiming in.

 

[tom baker]

If you are an electricians helper, part of the process of becoming an electrician is learning the NEC. When you become an electrician you will want to know what you are asking instead of going to a forum.
I will leave this post open for you to tell us where you have looked in the NEC.
I also hope your electrician is giving you some OJT

 

[Buck Parrish]

I agree with Tom - Unfortunately Pennsylvania does not offer a state wide electrical license. I know alot of the jurisdictions do require a license. But it's not near as strict as a statewide license, not even close.
Thus you will have guys that think their way is the right way, Even though they have never had to open a code book,
But mylk100 you can be different, some very smart electricians are from Philly and Pittsburg. Just stay on this forum, you'll see.