can I upgrade from mohave to macOS big sir

No. That model can't be upgraded past Catalina.

(203735)

The mid-2012 MacBook Pro is not compatible with macOS 11 Big Sur.

The newest OS that it can run is macOS 10.15.7 Catalina.

How to Upgrade  macOS:

The macOS version you can upgrade to depends on the model and year of your Mac.

Click the  (Apple) menu at the top left of your screen and choose About This Mac. 

❗️ – IMPORTANT – Backup your data, now, before you upgrade.

Learn How to Back up your Mac with Time Machine:

https://support.apple.com/en-us/HT201250

❗️ – IMPORTANT – Your 32-bit apps won’t work in Catalina or Big Sur.

https://support.apple.com/en-us/HT208436

Use this free utility to check the compatibility of your apps:

St. Claire Software – Go64: https://www.stclairsoft.com/Go64/

🖥 – Check compatibility of your Mac with newer versions of macOS.

https://support.apple.com/en-us/HT201475

✅ - Using Safari only, download the macOS upgrade installer app:

Click > Catalina.

Double-click the installer app in the Applications folder to begin the upgrade.

You're welcome.

FWIW, I am currently running Catalina on my own MBP 15" mid-2012 and I have no complaints about Catalina.

I will say I have an internal SSD and 16GB RAM, so that has a positive effect. 🙂

https://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade/DDR3_1600MHz_SDRAM

In fact, the RAM in the 2012 MBP can be upgraded. It has two slots, each capable of accommodating an 8GB module for a max of 16GB.

Best to let an authorized tech do the upgrade for you, however. 😉

Catalina is not slow, who told you that.

a Best Buy tech told me that about Catalina. I have a 2tb ssd Drive but only 8 gig of memory. Can I upgrade to 16 go on my pc

You cannot upgrade the RAM memory in a 2012 MacBook Pro.

Oh can you, oops then.

Thanks for the help

I know that feeling. I get it all the time. 🤪

You're welcome.