Oh yes also, we have a monitor from dell they is about 4 years old. Would we be able to use this with a new tower?
Probably. But you may have to change the connection type. Monitors and computers often come with 2 or more of the various ways to connect. Depending on which video connection type you were using between your monitor and the computer, if the new computer offers the same type of connection you should be good to go. If the offered video connections are different than your old computer then you would need to verify that connection type exists on your old monitor and acquire a video connection cable of that type. The various connection types over the years have been: VGA, DVI, HDMI, Thunderbolt, DisplayPort, USB-C.
And there are different versions (1, 2, 3, 1.3, 1.4, etc) of most of the above technologies.
So yea, PROBABLY but you may run into a mismatch that you will have to resolve.
To assure you can use it, figure out which connection type your monitor was using to connect to your old computer and make sure the new computer you choose offers that same video connection type.
Plan B would be to look at the video connection ports on your monitor (usually 2 or 3 are offered) and make sure your new computer supports one or more of those connection types and simply purchase the correct video cable for the connection type you choose to use. In some cases, there are different “plug” types at each end of the video cable that you MIGHT have to make sure are correct.
If you do get a new Dell computer there is a good/better chance your old monitor and video cable will work with the new computer without any of the above issues.