Why is there no focus indicator on the nikon d3200 camera? - 1

I own a D3200 nikon camera. I also own a lens AF nikkor 70-300mm for it… Which apparently does NOT auto focus.

Using the lens and the camera without auto focus. How do I know that the shot is in fact in focus, OTHER than (use your eye) are there indicators that still say "you are in focus" even if the lens does not auto focus itself?

P42 of your manual:

Focus.
To focus manually, adjust the lens focus ring until the
image displayed on the clear matte field in the viewfinder
is in focus. Photographs can be taken at any time, even
when the image is not in focus.
The Electronic Rangefinder
If the lens has a maximum aperture of f/5.6 or faster, the
viewfinder focus indicator can be used to confirm whether the
subject in the selected focus point is in focus (the focus point
can be selected from any of the 11 focus points). After
positioning the subject in the selected focus point, press the
shutter-release button halfway and rotate the lens focus ring
until the in-focus indicator (I) is displayed. Note that with the subjects listed on
page 36, the in-focus indicator may sometimes be displayed when the subject is not
in focus; confirm focus in the viewfinder before shooting.

In the future, if you want to be able to use the auto-focus feature on your camera, buy only Nikkor AF-S lenses. They have internal auto-focus motors.

Your camera does not have it's own focus motor. Your 70-300mm lens also does not have a built-in focus motor. Put them together and you lose AF. The D3200 will only AF with a lens that has it's own focus motor. With Nikon lenses, those are marked with AF-S, AF-I, and AF-P. AF only is not enough.

Dig the menu for something that means Focus Confirmation. This is an old feature that appeared in advanced Nikon film SLRs way back then. When you are in focus, there will be a dot appearing on the status screen in the viewfinder and at the same time, a beep will sound.

There's focus confirmation. A large dot will appear on the status screen in the viewfinder, sometimes accompanied by a beep. Check the manual if your camera has that feature and how to turn it on.

That's actually an old feature that came up even with the old Nikon AF film SLR's.