Can I make a 'Select' field into a 'Category' field?

For my coin and paper money catalogue, I created a field for "Country".  I didn't think in the beginning when I was setting my site up that I should have made the Country field a clickable link that would display all the items in that Country.  I can get the desired results of this if I put the name of the country in the Search field, but if it was possible, I'd also like to include this as a sorting option.

I'd like to know if it's possible to change a Select field type to a Category field type and not lose any data or have to enter a thousand (so far) entries manually by hand?

Thanks.

coincollection.dansmith.ca

no sorry i didn't think it possible with magical hand becausa category field use id not name for value
you can use your country field to display a text field search with multi value
1 edit your field
2 go to filter tab
3 choose an other diplay for this filter (multi select value)