There are lots of ways to do this but one of the easiest is with the effects package.

m1 <- lm(mpg ~ hp + disp, data = mtcars)
library(effects)
plot(allEffects(m1))

You can also do this with the sjPlot package, the ggeffects package, the marginaleffects package, or the emmeans package: see also How do I plot a single numerical covariate using emmeans (or other package) from a model? ...