I'm not a mod but I'm pretty sure that "can I get high off this" questions are not allowed on the board. If you're certain that what you have are Tylenol 3's, and want to use codeine recreationally, you best read up on how to do a Cold water extraction, which will prevent the liver damage that high doses of acetaminophen can cause.
Codeine is an opioid. It is addictive, like all opioids, and though it is one of the weaker ones I can say that it will nonetheless cause withdrawals if you get into a habit of using it and they're not too fun. If you have never used an opiate before, 30-60mg should have some effect. The lethal dose of Codeine is set at around 800mg, though I would not recommend going even close to that especially if its your first time. I started out on doses of 30mg or so, then it turned into 80, and eventually turned into 250mg as I used it more and more.
If you are used to a different opiate, like say oxycodone, you're probably not gonna find codeine worth much as a recreational drug. Some people hate it, some people love it.
Do not snort the pills or and do not under any circumstances try to inject them. This will not increase the high and can be very very dangerous. Codeine was made to be taken orally. As an oral drug it is converted into morphine and another opiate compound in the body, with much of the high coming after the drug has metabolized. Thus it takes awhile to kick in, say an hour or so. Some people's bodies cannot break down the pills into morphine which leads to a lack of effect.
I wouldn't honestly recommend getting into opiates at all, but obviously they are popular for a reason.
The other thing I'd say is that it's still risky taking pills if you don't know for sure what they are, the internet is not really a substitute for the bottle the pills come in.
Hope that helps.