Vegas Pro does not have a videoFX called jitter. You might want to have a play with the Film Effects VFX as that has a sort of a jitter control in it (to recreate very old film).

There does seem to be a jitter FX in Vegas Effects which is part of the VEGAS POST package. Jitter is mentioned under the Retro Glitch heading in:

https://www.vegascreativesoftware.com/us/vegas-post/vegas-effects/#productMenu

But Vegas Effects is only available as part of the VEGAS POST or VEGAS POST 365 package, not the standard Vegas Pro or Vegas Pro 365 products.

If you actually did get POST (which I don't have), you will need to access Jitter via Vegas Effects.

EDIT: Also, Jitter and Jitter Basic are the names of BorisFX video plugins, part of their BCC Time Unit. That BCC Unit has not been offered as part of any Vegas Pro offer in recent months. If you are after those specific FX plugins, you would need to purchase the Time Unit (or the whole BCC) directly from BorisFX.