You're probably missing a driver. I would do a Google search with "Ubuntu (version) laptop (brand and model) wireless driver", and see what that brings up. You can also check on the Ubuntu Community forums.
Check whether your machine is having a wireless card, if it does then it's the problem with the drivers, try installing them.
If it does not have the wireless card, then buy one and they come with drivers for different platforms/os
There're few adapters like TP-link nano series that even with the correct driver keeps not working correctly on Ubuntu (this from version 18.04) adriana#:)! could you tell me which version are you using?