Studio needs to have the install path from DIM set in the Content Directory Manager for DAZ Studio Formats and Poser Formats.
Edit: Open the Content Library tab (Window / Panes (Tabs) / Content Library if you don’t have one), if you can see your content here you may need to use the Content DB Maintenance options to clean up and re-import metadata.
Second Edit: With any of the older *.exe installers (frankly any installer) never assume the default install path is correct.. How you choose to pick your own install path will be different depending on the age of the installer. If you are trying to manually extract the files and folders from DIM zip be aware that there is a unnecessary ‘Content’ folder. Extract the files and folders inside the ‘Content’ folder.
It may help if you just grabbed any older *.exe and walked us through the steps you are taking.