Anybody practise shooting at cardboard deer targets??? any advice where I can purchase some??

Just use an old box and sketch one out. That's what I have done in the past. Dicks sporting goods has them for about $4.50 or so If you have one of the stores around you?

Just make sure that you put something solid behind it to stop the arrows because my 35# can easily go through card board like a warm knife through butter.

If you shoot thru them, the cardboard is rough on fletching, too.  We used to shoot thru silhouettes cut from bicycle and refrigerator boxes.

its good to put some hay bails or straw behind the cardboard or paper targets

I traced a projected image of a deer on a big piece of cardboard, then cut it out.  I use it as a template to trace out more.  Like everyone else said, put it in front of something that will keep your arrows from passing all the way through.