Convert all Environment files to '.Rda' and then load them at once with a loop

Here is a more automatic response, if you have many date frames and do not want to write the name of each one manually.

First part explaining how to save all the environment data frames:

# criar dados (apenas dois data frames no environment)
df1 <- data.frame(matrix(runif(12), nrow = 3))
df2 <- data.frame(matrix(runif(12), nrow = 3))
vec <- runif(12)
list <- list(runif(12), runif(12))

# obter os nomes dos data frames do environment
dflist <- names(Filter(is.data.frame, as.list(.GlobalEnv)))

# criar uma nova pasta para salvar os Rda's (showWarnings = FALSE para não mostrar os erros se a pasta já existir)
dir.create('dataframes', showWarnings = FALSE)

# salvar todos os data frames
for(i in dflist) {
  saveRDS(object = get(i), file = paste0('dataframes/', i, '.Rda'))
}

Now to read all saved frames automatically:

# lista com os nomes dos data frames
dfNames <- dir('dataframes')

# retirar '.Rda'
objNames <- sub('\.Rda$', '', dfNames) 

# ler os data frames
for(i in 1:length(dfNames)) {
  assign(objNames[i], readRDS(file = paste0('dataframes/', dfNames[i])))
}

Converts data.frames into list

df1 = data.frame(x=c(1:5))
df2 = data.frame(x=c(1:5), y=c(6:10))
df3 = data.frame(x=c(1:8), y=c(9:16), z=c(17:24))

lista_df = list(df1, df2, df3)

Save the list in the file lista_df.rds

saveRDS(lista_df, "lista_df.rds")

Loads list to file_list_new

lista_df_new = readRDS("lista_df.rds")

Converts list to data.frames

for (i in 1:length(lista_df_new)){
  assign(paste("df",i, sep=""), value = data.frame(lista_df_new[[i]]) ) 
}