Hi and welcome. The IRLB3034PBF is an N-Channel MOSFET in the TO-220 package, rated 40V breakdown, 343A, and a 2.5V threshold voltage. It is available online at Mouser.com showing 2995 in stock with 2000 on order. The IC is still in manufacture, and should be available from just about any quality electronics outlet, although you may have to order it. Assuming you are trying to build a
vape mod, there are any number of alternative parts that could be used depending on your application, but I am hesitant to recommend one without knowing this. I am not really an expert in these matters, although I have built a MOSFET
mod or two in my day, and I suggest you take a look in the modders forums on this board for more expert assistance than I can offer.