A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Assuming that all the street names are in a column, you can use a helper column that contains a cell formula that performs the substitution.
You'll have to think through the logic, but you can use a formula that looks at the 3 leftmost characters in the address for a space and the letters st and replaces them with the word Street.
You should investigate these formulas in Excel Help:
RIGHT
MID
FIND
LEN
CONCATENATE
Here's a video tutorial about Concatenate. Search the ExcelIsFun YouTube channel for more tutorials.
Excel Magic Trick 974: Formula to Join First & Last Name & Title: Ampersand or CONCATENATE?