The easiest way to do this would be to use the Flash Fill feature, as shown in the video lesson: Essential Skills Lesson 2-18 Use automatic Flash Fill to split delimited text.
Flash Fill was introduced in Excel 2013 so you will only be able to use it if you have Excel 2013 or a newer version (such as Excel 2016).
If you're not able to use Flash Fill, you can achieve the same thing by creating a column of ascending numbers and then using the concatenation operator (&) to append the letters "TB" to the number.
You can see how to quickly create ascending numbers in the video lesson: Essential Skills Lesson 2-14 Use AutoFill for text and numeric series.
For more on the concatenation operator, see the video tutorial: Expert Skills Lesson 3-18 Concatenate strings using the concatenation operator.
I have attached an example workbook showing this in action:
I hope this is the answer you were looking for, but please feel free to reply if you need any more help with this.
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