old pc running Windows 7 pro (64 bit) and need help to connect new HP Officejet 9120e printer

Windows 7 is no longer supported, and many new printers (including recent HP OfficeJet models) only provide drivers for Windows 10 and 11. If the manufacturer does not publish a Windows 7–compatible driver for the HP OfficeJet 9120e, the printer cannot be fully supported on Windows 7. However, the following steps can be tried to see if a compatible or generic driver works:

1. Check for a built‑in driver in Windows 7 (64‑bit)
   1. On the Windows 7 PC, select Start > Devices and Printers.
   2. Select Add a printer and follow the wizard.
   3. When the Install Printer Software page appears, look under Manufacturer for HP and see if any OfficeJet/DeskJet/Photosmart models are listed that are close to the 9120e.
   4. Select one and complete the wizard.
   5. In Devices and Printers, right‑click the newly added printer, select Printer properties, then on the General tab select Print Test Page.
   6. If the test page prints correctly, that driver is usable; if not, remove it and try another HP model.
2. Let Windows Update search for additional drivers
   1. In the Add Printer wizard, when the list of printers appears, select Windows Update (if available) to download an expanded list of built‑in drivers.
   2. After the list refreshes, repeat the steps above to try similar HP models.
3. Search for a WHQL‑signed 64‑bit driver If nothing suitable is built in:
   1. On the Windows 7 PC, select Start > Windows Update.
   2. Check for updates and install any optional hardware/driver updates related to printers.
   3. Try adding the printer again from Devices and Printers.
4. Check HP’s support site for any Windows 7 driver
   1. Go to HP’s official support site.
   2. Search for HP OfficeJet 9120e.
   3. If no Windows 7 driver exists, search for closely related OfficeJet models that might still offer a Windows 7 (64‑bit) driver and test them as in step 1.
5. Use a compatible emulation driver if no exact driver exists If HP documents the printer’s language (for example, PCL or PostScript), choose a driver for another HP model that uses the same emulation:
   1. In the Install Printer Software page, under Manufacturer, select HP.
   2. Pick another HP model that supports the same emulation (for example, another HP OfficeJet or LaserJet with PCL or PostScript support).
   3. Finish the wizard and print a test page.
   4. If the test page is unreadable, remove that printer and try a different emulation or model.

If none of these options produce a readable test page and HP does not provide a Windows 7 driver, the device will not be reliably usable from Windows 7. In that case, printing from a Windows 10/11 PC (where the official driver is supported) and sharing the printer from there is the practical alternative.

References:

• How to find a compatible printer driver for a computer that's running a 64-bit version of Windows
• Fix printer driver compatibility issues in Windows
• Fix printer not found and printer not recognized errors in Windows
• Fix printer connection and printing problems in Windows
• There is no Driver available on my HP Pavilion laptop for an HP Deskjet 2320 printer. How am I able to download a Driver? - Microsoft Q&A

Only the hardware manufacturer has the proprietary knowledge (and the legal right) to create drivers for their hardware. Thus, if HP doesn't make a Windows 7 driver for your printer, there isn't one.