I have an older MacBook Pro and am trying to determine its type number . It does not start up so cannot view it that way . On the back is model no. A1286. Can anyone help please ?

15-in model MacBook Pro.

That designator was used for models from 2008 through 2012, not including Retina 2012 models.

https://everymac.com/ultimate-mac-lookup/?search_keywords=a1286

All are capable for running 10.11 El Capitan, and some can run later versions of MacOS.

On models from before 2011, it may be very difficult to get an initial MacOS on board, but it can be done if you have another Mac available.

An "A1286" could be a 15-inch Late 2008 MacBook Pro model.

Ref: MacBook Pro (15-inch, Late 2008) - Technical Specifications

The hard disk drive is probably erased or corrupted or quite possibly failed.

Back that far, it’s also replaceable, if you want to spend money on a very old Mac.