Where can I see my troops stamina?

Do you mean the stats of the troops themselves or the durability of the APC?

The troops stats can be seen by tapping on the Command Center building and choosing the 'Troops' option. Here you can select one of the types of troops you have and tap the eye icon below it to see their stats. Stamina isn't one of the stats though.

If you tap the APC icon in the top left of the main screen or world map you will see the APC's listed and the remaining durability that they have is shown above each next to the tools icon. This will regenerate up to 100 over time.