How to remove files using find and rm command?

You need space between the command and \;

find -mmin -19 -exec rm {} \;

find already provide -delete option, so you don't need to use -exec rm ..:

find -mmin -19 -delete

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-delete

Delete files; true if removal succeeded. If the removal failed, an error message is issued. If -delete fails, find's exit status will be nonzero (when it eventually exits). Use of -delete automatically turns on the -depth option.

Warnings: Don't forget that the find command line is evaluated as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. When testing a find command line that you later intend to use with -delete, you should explicitly specify -depth in order to avoid later surprises. Because -delete implies -depth, you cannot usefully use -prune and -delete together.

You're missing an essential space to separate the braces from the semicolon.

find -mmin -19 -exec rm '{}' \;

but this does the same ting, is easier to type, and probably executes faster.

find -mmin -19 -delete