I founded a guide to upgrade from 2.x/3.x to 3.5
i followed the instructions and copy the upgrade folder to my sugar folder and replace one with the same name
then i write http://mysugardirectory/upgrade, then i click on next and i got this message:

the sugar folder version is 3.01a, only can upgrade to 3.0x
i try with 3.01b, and i have the same error
any idea?