Hi,
Are you connecting the printer via USB cable or network?
Have you tried using the printer's installation assistance on the Dell website?
https://www.dell.com/support/product-details/en-us/product/dell-b1265dnf/drivers
If not, download the Dell B1265dnf Mono MFP Software Suite and Driver and extract it to a folder. Run the setup.exe file as administrator.
Although this is not a Microsoft website, it is the official website for [Mb1265/Dell].
Thanks