My car is an Audi A3 2.0TDi S-line 140 2008/58 plate

I was wondering what size and make I should or could go for on all 4 brake discs and pads... Rear 2 are very low so thought I may as well upgrade on all of them whilst the chance is here

I have no idea about calipers or discs or anything I'm afraid
So it may be like talking to a complete idiot haha