due to my PC's 32 bit OS, I had to download blender 8.0 32-bit. After I tried to install an add-on on the face build, it didn't work saying "you are trying to install a 64-bit add-on into a 32-bit blender". Then I browsed a lot trying to find a 32-bit add-on but in vain. Can anyone suggest a solution, please?
This depends on the add-on you are trying to install.
Most add-ons are ‘python code’ only. Python is a programming language that is ‘text only’ and this means that it does not care whether it is running on a 32 or 64 bit system or whether on Windows, Mac or whatever - the code will still run regardless.
Some add-ons, however (such as Animation Nodes or Molecular) include additional libraries to perform some functions. These libraries have to be built for the specific system and it is those that are specific to 32 or 64-bit or Windows, Mac, etc. You need to contact the developer of such an add-on to determine whether a version exists for your particular system.