As per the Kuran-i Kerim, all Prophets (PBUT) identified themselves as Muslims, and all of their True Followers also termed them as Muslims!!!
2: 131. When his Lord said to him, "Submit (i.e. be a Muslim)!" He said, "I have submitted myself (as a Muslim) to the Lord of the 'Alamin (mankind, jinns and all that exists)."
2: 132. And this (submission to Allah, Islam) was enjoined by Ibrahim (Abraham) upon his sons and by Ya'qub (Jacob), (saying), "O my sons! Allah has chosen for you the (true) religion, then die not except in the Faith of Islam (as Muslims - Islamic Monotheism)."
2: 133. Or were you witnesses when death approached Ya'qub (Jacob)? When he said unto his sons, "What will you worship after me?" They said, "We shall worship your Ilah (God - Allah), the Ilah (God) of your fathers, Ibrahim (Abraham), Isma'il (Ishmael), Ishaque (Isaac), One Ilah (God), and to Him we submit (in Islam)."
2: 134. That was a nation who has passed away. They shall receive the reward of what they earned and you of what you earn. And you will not be asked of what they used to do.
2: 135. And they say, "Be Jews or Christians, then you will be guided." Say (to them, O Muhammad Peace be upon him ), "Nay, (We follow) only the religion of Ibrahim (Abraham), Hanifa [Islamic Monotheism, i.e. to worship none but Allah (Alone)], and he was not of Al-Mushrikun (those who worshipped others along with Allah - see V.2:105)."
2: 136. Say (O Muslims), "We believe in Allah and that which has been sent down to us and that which has been sent down to Ibrahim (Abraham), Isma'il (Ishmael), Ishaque (Isaac), Ya'qub (Jacob), and to Al-Asbat [the twelve sons of Ya'qub (Jacob)], and that which has been given to Musa (Moses) and 'Iesa (Jesus), and that which has been given to the Prophets from their Lord. We make no distinction between any of them, and to Him we have submitted (in Islam)."
2:140. Or say you that Ibrahim (Abraham), Isma'il (Ishmael), Ishaque (Isaac), Ya'qub (Jacob) and Al-Asbat [the twelve sons of Ya'qub (Jacob)] were Jews or Christians? Say, "Do you know better or does Allah (knows better...; that they all were Muslims)? And who is more unjust than he who conceals the testimony [i.e. to believe in Prophet Muhammad Peace be upon him when he comes, written in their Books. (See Verse 7:157)] he has from Allah? And Allah is not unaware of what you do."