Aid packages for downloading sims 3 extesion of the file appears as sims2.package . Even FrameworkSetup file. Sims2.Packages downloaded files appear here . I have also installed the sims 2. My OS is windows 7. Thanks .

Do you mean regular ".package" files, or the "sims2pack" and "sims3pack" files?

The TS2/TS3 package files showing up similar is common, particularly if you have SimPE installed, but doesn't influence the games as long as you put the right file in the right download folder. THey show the same because they have the same file extension. Make sure you keep the files separate so you know what belong to which game.

The sims2pack and sims3pack files should show as different.

my question is whether sims2packages files are compatible Sims 3 and that files for sims 3 files appears sims2packages

That just means your file associations are a bit off because the same file extensions are being used by different programs (TS2, TS3, and SimPE as mentioned). The game doesn't care about associations, some players see "PDF files" and other kinds of nonsense in that column and things work the same anyway.

The file associations dictate which program would open the file automatically if you double-clicked on them, which in this case you would not do unless you had a package file editor like S3PE or NRaas Packer installed and were trying to edit/create your own packages, and what kind of file icon might display on them which is equally as meaningless to the game.

Get Delphy's Dashboard. http://www.modthesims.info/download.php?t=387006

If THAT says you have a Sims 2 package in your game, it's an actual Sims 2 package and it won't work in Sims 3. Otherwise, EA likes the .package format. It's used for lots of games. They even used it for Spore. If it was made for Sims 3, it doesn't matter what other programs are set to attempt to open it. It will work in your Sims 3 game.

(Fun fact: If you try to open a Sims 3 file in SimPE, it will accuse you of trying to open a Spore file. This was because they came out with the Creature Creator, and it was discovered that SimPE was happy to try to open the Spore .package files, but couldn't figure them out. They had to add a function to prevent SimPE from trying to open packages that were not a Sims 2 file. )