where is my itunes sync backup in my pc

Where iTunes backups are stored on your computer

The folder where your backup data are stored varies depending on the computer's operating system. Make sure the backup folder is included in your periodic data-backup routine.

iTunes places the backup files in the following places:

• Mac:~/Library/Application Support/MobileSync/Backup/
• Windows XP:\Documents and Settings\(username)\Application Data\Apple Computer\MobileSync\Backup\
  Note: To quickly access the Application Data folder, click Start, and choose Run. Type %appdata% and click OK.
• Windows Vista and Windows 7:\Users\(username)\AppData\Roaming\Apple Computer\MobileSync\Backup\
  Note: To quickly access

http://support.apple.com/kb/HT4946

Thank you for this information. Question. I just made a back up of my Ipad and when to this location and could only see backups from 2015. I have been using itunes for many years, where are the old backups and where is the backup from 2016 from the ipad?

Unless you restored from a backup, when yo subsequently backup the previous backup is overwritten with the changes. Thus, typically you will only have one backup