You can use your existing license key to activate the new installation.
If you don't know your license key, plunk the email address that you used when you originally purchased Moneydance into the 'Lost Key' field of the following webpage so as to have the license key emailed to you. https://infinitekind.com/purchase
As for your data... I hope that you had a working backup routine in place.
Manual backup. A manual backup can be made under FILE (MONEYDANCE on Mac) – BACKUP EXPORT. The file naming convention is yourdatasetname-yyyymmdd-tttt.moneydancearchive
Automatic backup is set under FILE – PREFERENCES – BACKUPS. The file naming convention is yourdatasetname.yyyy-mm-dd.moneydancearchive
A moneydancearchive file is a compressed data set.
When you FILE – RESTORE FROM BACKUP a new data set is created with the naming convention – from manual backup yourdatasetname-yyyymmdd-tttt.moneydance the date time code taken from the backup file - from auto backup yourdatasetname (plus at number) e.g. yourdatasetname 2.moneydance The default data set location can be found under HELP – SHOW DOCUMENT FOLDER. You can rename a restored data set with Moneydance closed as you would any other folder provided you retain “.moneydance” extension. When you open Moneydance it will open in the “Welcome to Moneydance” window with the data set name listed on the right.