hi dear , my mac doesnt have any options for update software . so what should i do to update my software

Check the compatibility section of the following; if compatible upgrade using the instructions there: How to upgrade to macOS Big Sur - Apple Support

If not compatible with Big Sur, see the following from How to get old versions of macOS - Apple Support

If you want to check compatibility before downloading the installer, learn about the minimum requirements for macOS Catalina, Mojave, High Sierra, Sierra, El Capitan, or Yosemite. You can also check compatible operating systems on the product-ID page for MacBook Pro, MacBook Air, MacBook, iMac, Mac mini, or Mac Pro.