In phpMyAdmin there is a choice to export or import to a file. Use the export where I’m sure you will get a choice of an ‘.sql’ file (name it something recognisable and meaningful, this is the normal choice), or a ‘.csv’ (comma separated values file). The ‘.csv’ file is used with spreadsheet software, the other you know. I’m sure phpMyAdmin will place the file in your download folder, that’s why the importance of giving it a name that makes sense.
Export it as many times as you like, whenever. Import is just a reversal and will even recreate your database tables for you. Keep your backups safe and date them in a folder perhaps.