How to create a curve function

Question

I am getting acquainted with statistics and R and got stuck creating a curve() to fit my model. I am hoping someone could give me some insight on how to overcome that. This is my model:

Complete_Data_glmer2<-glmer(cbind(n_infected, Healthy) ~ 
         visit_rate_1000_per_yr * track_density + pop_density + 
         cane_toad1 + (1 | creek_id), 
         family="binomial", data =  taudactylus_rheophilus, 
         control=glmerControl(optimizer = "bobyqa", 
                              optCtrl = list(maxfun = 100000)))

I am trying to represent this information in a binary graph of presence/ absence of n_infected x the predictors.

Any help would be greatly appreciated. Thank you