To convert a database from older file format to the newer version .accdb file format, follow these steps:
1. Open the database.
2. Close any open objects.
3. Click to the file tab of the ribbon to enter backstage view and choose Save As.
4. In the ‘Save As’ dialog box, below the save database as heading, select access database (*.accdb).
5. Now click the Save As button.
6. Browse the folder in which you want to store the new version of your database.
7. After then assign a name for your database.
8. Access will creates new database containing all the objects in the old database, stored in the new format having extension .accdb. Additionally, a message appears you that this new database can’t open in access 2003 or earlier version.
9. Click ok.