New guy here looking for advice

Hey everybody, Mike here from southeast Idaho. I have an old Delorme pn-20 that I use at work to map school bus routes and personally for exploring around in the mountains. It still works great but I had to retire my old desktop at work (xp operating system) and I cant find maps for it to put on the new computer I now use. Does anyone know how I can get maps on my new computer so I can still do mapping with my pn-20? If not what would be a good handheld to replace it with? When I would go exploring in my Blazer I would take my laptop and have the pn-20 plugged into it so I had a nice big screen to use. I have an 8 inch fire tablet and an Ipad mini 5 and would like to use them with a handheld gps also. On the school bus side I would ride our routes and mark all the stops then download that onto my computer and draw the route out so I have nice maps for substitute drivers to use. I would take it with me on the 4 wheeler in the mountains and I liked to download the track when I got home to see where all I had been and also mark points of interesting things. These things would be my uses for a gps, looking for some advice on what to do.
Thanks!

 

Its been so long ago I don't really remember the sequence of events but I used the topo disc and put the program on my old computer and used that for drawing my routes. I don't remember if I had to load that map onto my pn-20 or if it was already on there. I did install the topo map disc on my new computer and when I go to the southeast Idaho area of the map and try to zoom in there is nothing there. I have never messed with the street atlas disc on either computer and yesterday I loaded the program on my new computer and it will let me zoom like I need so maybe that will work for me. I need to go run a route and see if I can get the info to show up on the street atlas program. If that works then problem solved.