Clarify keymap location and format in newbs_building_firmware.md (#24663)

docs/newbs_building_firmware.md

@@ -42,7 +42,7 @@ Look at the output from that command, you should see something like this:
 Ψ Created a new keymap called <github_username> in: /home/me/qmk_firmware/keyboards/clueboard/66/rev3/keymaps/<github_username>.
 ```
 
-This is the location of your new `keymap.c` file.
+This is the location of your new keymap file. Your keyboards default keymap file may be a `.json` file or a `.c` file.  If your keymap is a `.json` file it can be converted to a `.c` file using QMK's [`json2c`](cli_commands#qmk-json2c) utility. 
 
 ## Open `keymap.c` In Your Favorite Text Editor