It is and remains a secret how many vaults there are in the Fallout universe and where they were built. But the Amazon series gave new clues and a fan made a map out of it.
Vault-Tec has been busy and has built a fair amount of fallout shelters in the Fallout universe for the survival of at least some of humanity. A whole series of these vaults appeared in the games and, as is well known, Vaults 31-33 and 4 were added with the series.
But there was another juicy hint in the series about the location of other vaults. In one scene you can see a map of the Vault-Tec facilities and an advanced geography student has grabbed this new data to create a map of all the Vaults (really all of them) and has now published the project.
First, she used geographic information systems software ArcGIS Pro to georeference screenshots from the series, which essentially means she transferred the image onto a real map. These details could then be transferred to Google Earth to add additional reference points such as cities or state boundaries. She also added the vaults from the in-game maps of the Fallout games.
However, there are some uncertainties, because the map from the series in particular does not indicate whether the individual markings sometimes cover several vaults. We remember: Vault 31-33 from the series were connected to each other, so not far from each other.
If you want to explore the whole thing yourself, Nikki aka Tunnelsnakesfool is on their Discord server shared a file that you can upload to Google Earth for this purpose (download at your own risk). And there is also a video of the whole campaign: