Convert all number abbreviations to numeric values in a text file

Use numfmt from GNU coreutils, don’t reinvent the wheel.

$ numfmt --from=si <file
1300 apples
87900 oranges
156000 mangos
541700 carrots
1800000 potatoes

If abbreviated numbers may appear as any field, then you can use:

numfmt --from=si --field=- --invalid=ignore <file