Really? look at the bolded parts.
B. STEPS PREPARATORY TO INDEPENDENCE
A Commission shall be set up consisting of one representative of each of five Member States. The Members represented on the Commission shall be elected by the General Assembly on as broad a basis, geographically and otherwise, as possible.
The administration of Palestine shall, as the mandatory Power withdraws its armed forces, be progressively turned over to the Commission, which shall act in conformity with the recommendations of the General Assembly, under the guidance of the Security Council. The mandatory Power shall to the fullest possible extent coordinate its plans for withdrawal with the plans of the Commission to take over and administer areas which have been evacuated.
In the discharge of this administrative responsibility the Commission shall have authority to issue necessary regulations and take other measures as required. The mandatory Power shall not take any action to prevent, obstruct or delay the implementation by the Commission of the measures recommended by the General Assembly.
On its arrival in Palestine the Commission shall proceed to carry out measures for the establishment of the frontiers of the Arab and Jewish States and the City of Jerusalem in accordance with the general lines of the recommendations of the General Assembly on the partition of Palestine. Nevertheless, the boundaries as described in Part II of this Plan are to be modified in such a way that village areas as a rule will not be divided by state boundaries unless pressing reasons make that necessary.
The Commission, after consultation with the democratic parties and other public organizations of the Arab and Jewish States, shall select and establish in each State as rapidly as possible a Provisional Council of Government. The activities of both the Arab and Jewish Provisional Councils of Government shall be carried out under the general direction of the Commission.
If by 1 April 1948 a Provisional Council of Government cannot be selected for either of the States, or, if selected, cannot carry out its functions, the Commission shall communicate that fact to the Security Council for such action with respect to that State as the Security Council may deem proper, and to the Secretary-General for communication to the Members of the United Nations.
Subject to the provisions of these recommendations, during the transitional period the Provisional Councils of Government, acting under the Commission, shall have full authority in the areas under their control including authority over matters of immigration and land regulation.
The Provisional Council of Government of each State, acting under the Commission, shall progressively receive from the Commission full responsibility for the administration of that State in the period between the termination of the Mandate and the establishment of the State's independence.
The Commission shall instruct the Provisional Councils of Government of both the Arab and Jewish States, after their formation, to proceed to the establishment of administrative organs of government, central and local.
The Provisional Council of Government of each State shall, within the shortest time possible, recruit an armed militia from the residents of that State, sufficient in number to maintain internal order and to prevent frontier clashes.
United Nations General Assembly Resolution 181 - Wikisource
When did all this happen? It didn't. Palestine was never partitioned and no state was established.