Question

it was a beautiful garden( use the noun form of beautiful)

Answer 1

The same sentence can be written in many ways using the word 'beautiful' as 'noun'.

The noun of 'beautiful' is 'beauty'.

So we can use 'beauty' in sentence as shown below:

The garden was of immense beauty.

or

The beauty of the garden was amazing.

or

The garden was of inexplicable beauty.

or

The beauty of the garden amazed me.

And so on...

Answer 2

The answer will be ‘The garden was a sight of beauty’.

The noun form of the word beautiful is beauty. In order to keep the meaning of the sentence same, we can use the word beauty instead of beautiful.

Hence the reconstruction of the sentence is needed, which has not hampered its meaning or the mode of sentence at all.