i need help
 

what kind of plywood do i need to get the only stores around here is umm lowes and homedepot

How about Michel's or Hobby Lobby? They usually have various thicknesses of plywood and so forth.
My local Lowe's and Home Depot don't carry what you need.

oh ya we have a hobby lobby what should i get though im building a 40" cargo ship

You will probably have to splice the keel due to lack of length but I'd start with 1/4 for that and 1/8 for any cross frames. Your best plywood for boats are 3ply 1/16 for skins, 5 ply in 1/8 and 9 or so in 1/4. I use birch ply with spruce for stringers and glue blocks when I build.

whats a stringer and a glue block could i get a pic please

I used to use aircraft grade plywood in 1/8" for skin and frames and 1/4" for engine rails and transom on gasser boats,but with it's price increase and shipping costs I haven't been building for a while.I used to buy from Aircraft Spruce as you can get 24" x 48" where as the other companies mostly have 12" x 48" and sometimes you can't get too many parts on a piece that size and have waste.I like to get parts laid in really close to each other to avoid excess waste.I've found 1/8" and 1/4" birch 3 ply plywood at a local building center at a good price for a 4'x8' sheet.It's got a nice sanded surface on one side,but would have to be sealed really good.
They also have sheets of a white plywood that one sheets bends width wise and the other sheet bends length wise .This stuff can be bent in a circle.I've tried lauan plywood but it doesn't bend too easily before it starts cracking,plus it splinters on the edges.

Whatever it gets made of, it will need some form of protection/sealing to either protect it from the elements and/or look like you intended and keep it that way. This applies to everything from paper to sheet steel and all points between going via wood and fiberglass.
For a cargo boat that size, 1/8 for most of the skin, I assume that in your home improvement stores there is a section with small section wood strips - 1/4x1/4 makes good framing and joining reinforcement for corners. My first ones got their raw material from the panels of a dead kitchen door.