To answer your question. Yes you can plug the usb port into your Dell and it will send power to the phone without messing up the phone or the computer.
If you aren't getting any charge your may have buildup in the port from pocket lint, dust, etc. There are guides online of how to safely clean this out without shorting out the port, and you can find them by typing your phone make and model + cleaning out charging port. Since this is the internet I will warn you to use common sense and don't follow any that say wash it out with water or to use a metal pick.
Other than that I know micro usb has a habit of wearing out over time and your port may just be reaching toast. If this is the case, some phones, not all, have wireless charging capabilities so you might be able to get a little induction puck (made for your phone) and set your phone on it and it will charge wirelessly.