library(stringr)

  string1 <- ("536.2k Followers, 83 Following, 1,396 Posts")
  string2 <- ("5m Followers, 83 Following, 1.1m Posts")

  info <- str_extract_all(string1,"[0-9]{1,5}(?:[,.][0-9]{1,4})?[mk ]?")
  info2 <- str_extract_all(string2,"[0-9]{1,5}(?:[,.][0-9]{1,4})?[mk ]?")

  info 
  info2