Drivers can be found here
HP DeskJet 3745 Drivers Are you looking for Windows 10 drivers? If so, I'll suggest trying the Windows 8.1 driver, it may work otherwise HP says to use Windows Update to find the drivers. HP also states they have not tested the printer for compatibility with Win 10.
Hope this helps some.
edit: it appears my HP link is not working proper (at least for me) let me know if you experience problems with the link