Sorry but you said it was a MacBook Pro and there were no 11" Macbook Pros in 2015. see https://everymac.com/systems/by_year/macs-released-in-2015.html
It looks like you may have a MacBook Air? Do you have icore5 or icore 7? it should state that it is a 7.1 model?
Alternatively is it perhaps a MacBook 12"
As to Memory - I am checking but suspect you will need 8GB and you have only 4GB - normal with MacBook Air!
How much Disk space do you have 128 or 250 GB SSD are normal on each but 128 may not be enough for Big Sur and whatever oyu want to do, unless oyu use an external for backup?
So, first find out which one it is Everymac is good for that.
NB you may be well advised to up your OS step by step to Santa Catalina and go from there to Big Sur. Its a big jump from 10.10 to 11.0.1 You might go via Recovery - Restart holding down Cmd and R and it will give oyu several useful options including update OS?
Hope this clarifies the situation?
Colin