I have 3 devices and not 1 will allow me to download base camp any ideas or there's navigator 6 going cheap

You don't download BaseCamp to your device, you install it on your PC

I know that when I down load it then try to open its says file cannot be opened so it's up for sale along withe the docking mount

Sorry but its not clear from your post what you're trying to do and what is failing so can't help unless you clarify the problem you're having

I'm trying to upload/ download garmin basecamp/ express to my tablet or laptop so I can plan rides a nd sync them to my nav6

When I try to download or install it's says download complete  yet when try to continue it says can't open file so I'm not able to view what is on offer

navigator 6 up for sale with base plate

will stick to my tomtom rider

You could try downloading the installer from GPSrChive (click on the Software Updates on their site). Or right click on your download and choose Run As Administrator to see if that makes a difference.  From GPSrChive you can also try an older version of the software - many people still use 4.6.2.