How to make a conveyor belt with LEGO parts?
You will need to decide between 3711 Technic Chain Link and 3873 Technic Chain Tread, or possibly use them together.

Each link of chain is about 1 cm long and 0.8 cm wide

 and you can get them in packs of 108 (Chain Link Set Product Code: 2000645)

 

The Chain Tread are wider, 

but seem to be available only in smaller packs, such as
Set # 9938-1: Conveyor Belt Links (Nominally 36 links)
Set # 1149-2: Bulldozer Chainlinks  (nominally 52 links)