for(i in 10:13) {
    nam <- paste("mu04mun_", i, sep = "")
    d <- paste0("sub04mun", i, "$des_flo_04")
    assign(nam, qnorm(d))
}

d <- "texto"
qnorm(d)
#> Error in qnorm(d): Non-numeric argument to mathematical function

for(i in 10:13) {
    nam <- paste("mu04mun_", i, sep = "")
    d <- paste0("sub04mun", i)
    assign(nam, qnorm(d)[["des_flo_04"]])
}