Migrate from another footnotes plugin?

For two related sites (together they publish hundreds of standard WP pages), I have been using a footnotes plugin that no longer works with recent WP updates.

Is there a way to substitute its start-and-end shortcodes with yours to eliminate the time and trouble of manual replacement?

I have a “global search and replace” plugin. Is it safe to use it for this purpose? If so, I will need step-by-step instructions for how to style elements like “sup” and other font spex.

Many thanks, Anna