Anyone know what size tubes and tires to get for a Women's 15in Giant cypress dx 6016? The bike is older, I'm guessing 2006-2008 but I'm not positive.
Without photos or other details, it's a bit hard for us to tell, since the wheels may not be original, etc. Often, your best bet is to find a well-regarded local bike shop and ask them. You may need bicycle repair in the future, perhaps in a hurry, so this is a good opportunity to find a shop you're comfortable with.
Searching on the net, I did find an old ad for a used https://sidelineswap.com/gear/bikes/complete-bikes/other-bikes/2525465-giant-cypress-dx-hybrid-bike-15-in-frame-24-speed-nice which may be the type you have. It seems to have 700C size wheels.
bikepedia.com is a good resource for bike specs by year, make and model.
Presumably you want tubes and tyres for a new-to-you bike, and want them to fit the existing rims.
The sidewall of the tyre will have some numbers written there. If Armand is correct, then there will be something like "622-35" or possibly reversed. This is a standard format called ETRTO.
The 622 is your rim size, and the 35 would be the tyre's width, both in millimetres.
Other possible numbers include 559 (the common 26") and 630 (an obsolete
27 or 28 inch which was neither)
If you're getting a bike with rims but no rubber at all, then it gets a bit harder. How to determine tire size when the sidewall label is unreadable?
If you're buying spares, in case you need them, then wait till you get the bike in your hands. There's always a chance someone has modified something, or the model year quoted was off.
Patience - you'll be riding soon !