Tip! To find the menu number of a menu, select that menu using the keyboard, the pull down menus and the (NXT) key. Then type the RCLMENU command to get the menu number. This is a number in the form (...)
But that explanation is not clear to me
I can't get the Base menu, for instance (RightShift+3).
Those instructions only work when "Soft MENU" mode is turned on. Press [MODE] [FLAGS] (that's on the F1 key) and then press the up-cursor key until flag 117 is highlighted. If it says "CHOOSE boxes", then press [F3] to toggle it to say "Soft MENU" instead. Press either [OK] (on the F6 key) or [ENTER] twice to return to the normal stack display.
Now display any soft menu you wish (e.g. the BASE menu), and then type RCLMENU (using ALPHA mode of course) and press ENTER. The menu number of the currently displayed menu will be returned to the stack.
Hope that helps! Disclaimer: I don't work for HP. I'm just another happy HP calculator user.