Q: what os x

There are no Macs with that model number; the maximum OS for a 2007 MacBook(these have a model number of A1181) is Lion 10.7.5.

(142881)

If yours is a mid/late 2007 it should be upgradeable to 10.11.5 but RAM needed for that system is a minimum of 4GB (8GB more realistic).

OS X El Capitan - Technical Specifications

However, given the age of your MacBook, 10.6.8 is a good stable OS.

  Lion

Check to make sure your applications are compatible. PowerPC applications are no longer supported after 10.6.      

Application Compatibility

Applications Compatibility (2)

El Capitan 10.11 Compatibility information

Also check to make sure there is a compatible driver for your printer.

Do a backup before installing, preferable 2 backups on 2 different drives.