Yes, there is a formula in Excel that can convert numbers from base 36 to base 10. The formula is called "BASE" and it takes two arguments: the number you want to convert and the base it is currently in. Here are the steps to convert your transaction numbers from base 36 to base 10:

1. Open your Excel spreadsheet and select the cell where you want to enter the formula.
2. Type "=BASE(number, 36)" into the cell, replacing "number" with the transaction number you want to convert.
3. Press Enter to calculate the result.
4. Repeat steps 2 and 3 for each transaction number you want to convert.

If you have 30,000 transaction numbers to convert, you can use Excel's "Fill Down" feature to quickly apply the formula to all of the cells in a column. Here's how:

1. Enter the formula into the first cell in the column, as described above.
2. Click on the cell to select it.
3. Move your mouse to the bottom right corner of the cell until you see a small black cross.
4. Click and drag the cross down the column to apply the formula to all of the cells.

Excel will automatically update the formula for each cell, using the correct transaction number. Once the conversion is complete, you can copy and paste the results into a new column or spreadsheet if needed.