Is merrily a noun pronoun or adverb?

The word 'merrily' is the adverb form of the adjective 'merry'.

The adverb 'merrily' modifies a verb, an adjective, or another adverb.

The adjective 'merry' modifies a noun.

Example: She hummed merrily as she worked in her garden. (modifies the verb 'hummed')

A noun is a word for a person, a place, or a thing. The noun in the example sentence is 'garden'.

A pronoun is a word that takes the place of a noun in a sentence. In the example sentence, the pronoun 'she' takes the place of the noun or name for the person spoken about; for example, "My neighbor hummed merrily...", "My mother hummed merrily...", "Thelma hummed merrily...", etc.