I thought there was a Mudcat thread on this song, but I guess not. You'll find lyrics at https://www.mamalisa.com/?t=es&p=4235:

Down on Grandpa's Farm
Children's Song

(Chorus)
We're on our way,
We're on our way
On our way to Grandpa's farm.
We're on our way,
We're on our way
On our way to Grandpa's farm.

Down on Grandpa's farm
There is a brown and white cow,
Down on Grandpa's farm
There is a brown and white cow.
The cow,
She makes a sound like this:
"Moo, moooo!"
The cow,
She makes a sound like this:
"Moo, moooo!"

(Chorus)

Down on Grandpa's farm
There is a little pink pig,
Down on Grandpa's farm
There is a little pink pig.
The pig,
She makes a sound like this:
"Oink, oink!"
The pig,
She makes a sound like this:
"Oink, oink!"

(Chorus)

Down on Grandpa's farm
There is a little green frog,
Down on Grandpa's farm
There is a little green frog.
The frog,
He makes a sound like this:
"Ribbit, ribbit!"
The frog,
He makes a sound like this:
"Ribbit, ribbit!"

(Chorus)

There's a YouTube recording by Raffi of this song here:

https://www.youtube.com/watch?v=uwyeOi9EH9I