restoring safari history

Hi

Have lost all safari tabs going back months- computer closed down and then it was reopened without restoring whole history and it's lost the whole lot. Desperate to get tabs back. Have read here it's kept in ~/Library/Safari/History.db, History.db-shm, History.db-wa but have no idea how to access this - not very computer literate. Can anyone help? Need step-by-step instructions....