I am planning to upgrade my RAM in my laptop, but I’m not sure if I have to backup my computer.
Totally agree with Jeffery. A backup is good to have, but upgrading your RAM should not do any damage to your installation or your stored data. Just don't throw the computer on the floor.
It never hurts to make a backup before you tamper with hardware, however you risk no real damage to the hard drive when changing the ram. In the case that the ram you install doesn't work, swap it back out for the other and you're back online.