Question

when the United Nations officially came into existence

Answer 1

A replacement for the ineffective League of Nations, the organization was established on 24 October 1945 after World War II with the aim of preventing another such conflict. At its founding, the UN had 51 member states; there are now 193.
☺️hope it helps☺️

Answer 2

$\underline { united\: Nations \:officially\: existence}$

After ending of firat world war NO(rastra sangh) was established to maintain peace in world but it was unable to maintain it so in 1939 second world war was fought in 1945 after ending of second world war UNO was formed in place of NO to maintain peace among all the member countries.

$\red{Establishment\: of\: UNO}$ :-
UNO was established in 24 October 1945.
history of UNO:-
in the very starting of UNO there was 51 countries in UNO .

$\green{Current\: countries}$:-

there are 193 countries in the UNO among all the 195 countries in the world the latest member of UNO is south Sudan.
india became member of UNO on 31 october 1945.

$\red{Purpose \:of \:UNO}$ :-
The central purposes for which the U.N. was established -- to maintain international peace and security; to foster cooperation in solving international economic, social, cultural, and humanitarian problems; to promote respect for human rights and fundamental freedoms; to develop friendly relations among nations; and to .

$\green{Parts\: of \:UNO}$:-

Security Council.

Secretariat. Secretary-General. 

General Assembly. President.

Economic and Social Council.

International Court of Justice. {headquarter is in THE HEG (Netherlands)}

Trusteeship Council.

☯️ The current President of UNO is ANTONIO GUTERES.

● hope i helped u ●