Export ALL data from CRM

I am fairly new to CRM and originally imported records as accounts and contacts when I realise they should have been leads. 

I want to export them and re import them. 

When I tried only the fields that were exported were the ones on view in CRM at the time.

Of course I want to export all the fields, then delete all contacts and accounts on CRM and re import as leads.

 Any help would be appreciated. Thanks