Its quite simple, Use paste function as below.
Where l = list(1:3) or c(1:3)
> lapply(l, function(x) {paste("I scored",x,"marks in Exam",sep = " ")})
[[1]]
[1] "I scored 1 marks in Exam"
[[2]]
[1] "I scored 2 marks in Exam"
[[3]]
[1] "I scored 3 marks in Exam"