How to get database in new created SSMS sql server developer edition but I don't have back up of database but mdf file and ldf file are available.
If you have the mdf file, you have your data. Re-install the SQL express edition, attach the database file take a backup and restore it to your developer edition, see Restore database according to editions if you have issues with the restore.
If you don't have the mdf file and you don't have a backup, it is gone, start over.
When you installed developer edition, if you created a database with the same name, and put the mdf and ldf files in the same place as the old SQL express edition, then you overwrote the mdf files and your data is gone.
thank you for your answer but I solved It out by using this link https://support.resellerclub.com/helpdesk/index.php?/Knowledgebase/Article/View/260/5/steps-to-attach-mdf-and-ldf-files-of-mssql-databases-to-convert-it-to-bak-format