There is no direct metro line between these two stations.
One can take the Green(Linha Verde) and Blue(Linha Azul) Metro lines between the two, changing at Baixa Chiado Station.
Carris.pt 758 bus runs directly between Sete Rios Station and Cais de Sodre Station.
Every 10 minutes during the day. Transit time depending on traffic about 35 minutes & one gets to see Lisbon.