What she means is that she had made 19 trips to Maryland, helped 300 people to freedom, yet she was never captured and didn’t fail to deliver her "passengers" to safety. As Tubman herself said, "On my Underground Railroad I [never] run my train off [the] track [and] I never [lost] a passenger." During these journeys she helped rescue people that were from her own family and people who weren’t from her own family. You can check her story in the America Library.
She should persuade her audience by including benefits of the trip to Washington D.C, historical facts, and locations. Also, New York can be used to compare to Washington D.C, so there is more opportunity to persuade the audience in going to D.C. I hope this makes sense, i may just me terrible about explaining, but i hope i kinda helped
