There are 7 snowglobes in game (DLC excluded) located in different places. This guide will show the detail locations of all the 7 snowglobes.

The snowglobe is on the left grave. Easy to find.

The snowglobe is right on the welcome desk.

Old Mormon Fort is inside the Freeside. Trave to the Freeside North Gate first and enter the Fort. The snowglobe is on your right side, a shelf on the observation tower.

After entering the Jacobstown, go straight forward to the lodge. It's right on the reception desk.

Travel to Nellis Air Force Base first and look for the Boomer Museum. Right on the desk..

Go the lucky 38 where the Mr.House is located. Take the lift to Cocktail Lounge. The snowglobe is behind a green lamp.

Vault 21 is right after entering the second NV Strip gate and you can see the Vault 21 Hotel. Go in the Workshop looking for Sarah's room. It requires a Lockpick of 50 or you have to steal the key to get in.