Is this the really long level with the red baby Yoshi? Yes, it's quite frustrating. There is a place with a long low tree top and just below it you might be able to see pink or green blocks. There is a key down under there. I don't think you will need Yoshi to get the key, but you will likely need him to pass the level. I usually go to one of the other star levels, grab a purple Yoshi, and fly most of the way over this level. You can still fly with red Yoshi when you eat a purple shell, but red Yoshi spits out fire instead of setting the shell down.

yo i get that but which tree is it cuz i saw it before but now i can't find the box i tried so many times help me im stuck

Get a cape and fly until u see a legde,stop onto it there should be a green shell,grab it and take it to the ledge below thow it at the ? box,dogde it and a key should come out,put it into the keyhole next to it and there you go.

which level is that? One star level requires that you go up in a cloud, one that you go under the first exit under water, one that you allow the coins to turn back into blocks, and two more.