Ecole Militaire to Gare du Nord

My first trip to Paris is fast approaching. At the end of my time in Paris, I'll need to get from the Ecole Militaire Metro station to Gare du Nord. It looks like I would need to do the following: - take line 8 from Ecole Militaire toward Creteil
- transfer to line 4 at St. Denis toward Porte de Cligancourt and exit at Gare du Nord Am I reading the Metro map correctly? Any idea how long that trip will take? Thanks!