Sure, I can help you with that! Here's how you can convert the number 345,000 to the million currency format of .345 MM in Microsoft Excel:

1. Select the cell containing the number you want to convert to million currency format.
2. Right-click on the cell and select "Format Cells" from the drop-down menu.
3. In the "Format Cells" dialog box, select the "Custom" category.
4. In the "Type" field, enter the following format code:
   Code:

   0.000,," MM"

5. Click "OK" to apply the format to the cell.
6. The number 345,000 should now be displayed as .345 MM in the cell.

That's it! You have successfully converted the number to million currency format. If you have any other questions or need further assistance, feel free to ask.