[philso]

Welcome to Chief Delphi.

You will have to draw a diagram showing the location of your gearbox in your robot, the point you attach the winch cable to, etc. They you need to do some math to calculate what torque will be applied to your gearbox. Then, get the specifications for the gearboxes you are considering and compare the torque ratings to the torque you have calculated. This is a STEM program and due to the large forces involved in winching your robot off the ground, you are very likely to be disappointed with the results if you don't do these calculations and destroy your gearbox. Please note that many of the high-ratio gearboxes have quite a low torque limit.

If you need guidance on how to do all of this, post here showing what work you have already done (diagrams, calculations) and ask for help. Your school's location at Bloor and Dufferin puts you in the middle of many experienced teams that should be able to help a rookie team like yours.