Fleets can carry an invasion force whose size is equal to the number of cargo holds in the fleet. Each of your Carracks has three cargo holds. Therefore, one of your ships will be able to carry the three Pikemen you made in the last episode.
Those three Pikemen are pretty tough, and have a good chance of success. However, they may be defeated and have to retreat back to your own land. If you decide to send a larger force, you will have to send more than one ship.
Remember not to move the last ship out of your home fleet. Although you can de-emphasize trade while conducting your invasion, at least one ship should remain behind for sea transport and/or a minimal amount of trade.
