The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.
Does this computer appear as listed to Qualify for anything newer than High Sierra macOS 10.13 ?
Answer, No !
That means this computer has been Deemed by Apple as not having the required Hardware to Qualify for anything Newer
You will need to shop for a new or Newer Computer that does qualify for a newer version of macOS
Certified Refurbished Products - Apple (CA) at a lower cost
Apple Trade In - Apple (CA) and the value of your present computer is put towards the cost of a New Computer
The Trade In I have used several time for Both Apple Computer an Apple iPhones and it has worked very well for me.
Actually, just finished a Trade In of an iPhone 12 mini for a New iPhone 14
Computer Qualify for the Monterey upgrade
macOS Big Sur 11 hardware requirements
macOS Catalina 10.15 hardware requirements
macOS Mojave 10.14 hardware requirements