I think your confusing 2 different things.
The tires might be 16 inch and that could probably work on your vehicle but but you need to know the spec for the tire. 16 inch only refers to the inside measurement of the tire. Like is it a 275/ 65/ 16 etc. Long story short, keep the overall outer diameter about the same. At the very least, you want to make sure your 4 tires are all the same size. If you start getting too much difference then you're going to see it start to throw your speedo off.
The rims your friend has might be 5 hole but you have to measure the distance between the wheel studs to make sure it fits. So lets say your van has PCD 114.3mm. Or pitch center diameter of 114.3mm across. If the other rims have the studs farther apart or closer together, just because they have 5 holes doesnt mean they will fit.
Then there's that lip on the hub itself which is bore size. Lets say that your van currently has a 60.1mm bore. If the rim you are looking at is smaller, it simply wont fit over that larger lip on the hub.
I would suggest take a few minutes and do a google search on things PCD, hub size, bore size, how to check rim or tire size etc. Yes, you can ask your questions here but doing it yourself through google will provide you faster, more detailed answers to better educate yourself with what works.
At the very least, if you want to ask on here what works then you need to post the dimensions of both rims and tires on here so others can get you an answer.
Hope that helps.