You can use BigFloats to increase the precision and also use setprecision() to tweak it manually. To plot the results, you can use one of the many plotting libraries out there (PGFPlotsX.jl, Plots.jl, Gaston.jl, Makie.jl, UnicodePlots.jl, …).
I am not sure where you struggle to be honest, given that the code snippet you provide is neither working, nor is it self-descriptive. Anyways, I think both of your questions are answered now 
Btw. you can quote your code to make it more readable (here is a quick guide how to make it easier to help you: Please read: make it easier to help you)