Welcome to Android Central! Which Xiaomi phone? If there's no official system update available through the system settings, then check Xiaomi's support page for that particular phone. If you don't find an official update there, then your only option would be to root the phone and see if there are any custom ROMs available based on a higher Android version. The forums at XDA-Developers.com would be a good resource for that kind of thing.
Thank you! It is a Xiaomi Note 5a, the Note 5a with the finger print sensor on the back. I'm worried if the phone's hardware wouldn't be able to handle a newer version of android hence why Xiaomi stopped giving it 'android' updates.
It's a 3 year old device -- most companies only support their devices with updates for 2 years at the most (and that's typically just for flagship devices). It's not always a question of the hardware.