Select the thumbnail and click Export (bottom left)
Choose your format e.g jpeg, color space e.g sRGb and size width and height or just choose long edge, with resolution of 240 or 300 for printing.
In LR you don't have to SAVE or EXPORT an image to print it with the adjustments/edits you have done to it. LR applies the adjustments/edits when it sends the file to the printer.
That I know. I guess the best way for me to explain is after I have printed I want to save it for future prints.
The Edits never go away. That is if you have written them to an XMP sidecar file or you have multiple backups of the catalog and your images including the XMP file.
Just because you have printed it doesn't erase the edits, the way the images looks.
If you chose to Re-Edit it you can do that to a Virtual Copy which will preserve the original edits.
In any event I wouldn't Export as a JPG if you chose to do that. I'd export as a TIFF file with either Adobe RGB or Pro-Photo color space.