I guess you don't have any backup... Well, searching "unrecognized database format mdb" w/o quotes in Google, you should find valuable guides and tools to repair it.

to refer below url i think you can get valuable answer

https://support.microsoft.com/en-us/kb/257780
https://social.msdn.microsoft.com/Fo...orum=accessdev

Try this sequence in order below or as an additional resources for restoring .mdb file see and learn following topics, and in case your corruption is severe, one more solution must assist you

http://forums.techguy.org/windows-8/...e-copying.html
http://www.sqlservercentral.com/Foru...376-384-1.aspx
https://onlinefilerepair.com/en/acce...ir-online.html

Try this sequence in order:
1. Backup.
Make a backup copy of the bad database, without overwriting any existing backups. Whatever has gone wrong, you don't want to make it worse, and a backup gives you multiple attempts at recovery.
2. Uncheck the Name AutoCorrect boxes.
In Access 2007: Office Button | Access Options | Current Database.
In previous versions: Tools | Options | General.
For an explanation of why, see Failures caused by Name Auto-Correct.
3. Compact.
In Access 2010: Compact and Repair Database on the Database Tools ribbon.
In Access 2007: Office Button | Manage | Compact/Repair.
In previous versions: Tools | Database Utilities | Compact/Repair.
4. Decompile.
Close Access, and enter something like this at the command prompt:
"c:\Program Files\Microsoft office\office\msaccess.exe" /decompile "c:\MyPath\MyDatabase.mdb"
Use the path to where msaccess.exe is found on your computer, and include the quotes.
5. Compact again.
Open Access (holding down the Shift key if you have any startup code), and compact again.
Do this twice: one compact does not work in all versions (unless you close Access between step 4 and 5.)
6. Set minimal references.
Open a code window.
Choose References from the Tools menu.
Uncheck any references you do not need.
For a list of the ones you typically need in your version of Access.
7. Compile.
Still in the code window, choose Compile from the Debug menu.
Fix any errors, and repeat until the code compiles okay.
8. Set code options.
Still in the code window, choose Options on the Tools menu.
On the General tab, make sure Error Trapping is set to "Break on Unhandled Errors", and Compile On Demand is unchecked.

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