When choosing a crate it is best to pick the crate that will fit your puppy at maturity so that you don't have to buy multiple crates during your dogs' lifetime. I also would suggest purchasing a divider to go in the crate so that it is small enough for when you first get the puppy. You can gradually expand their space as they grow but remember to only leave enough room for them to turn around and lay down. You don't want them to have too much space or you may come home to some potty accidents. Below is a chart you can refer to in choosing which crate size will be best for your new pup!
Size Length Puppy Weight Range XS 19" <20 lbs S 24" 20-30 lbs M 30" 30-40 lbs L 36" 40-70 lbs XL 42" 70-90 lbs 2XL 48" 90 lbs +