how can i use my imac display with my dell laptop

+1 and I think what Allan is also trying to tell you is to buy an external monitor for your Dell if you need the additional screen real estate.

Please remember the Macs are computers, they are not external displays for other devices.

You can't. Target Display Mode was Mac-to-Mac. Apple never intended, supported, or documented its use on other devices.

TDM is a dead issue. Apple removed the ability of iMacs to act as a second display source in Late 2014. Then they removed the ability of Macs made after 2019 to use an iMac as a second monitor.

Even the support article in now archived and not receiving updates about newer macOS versions and Mac models.