How is the zakat calculated for an ornamental jewelry set that has not reached the nisab, and a year has passed since the engagement was broken off, along with money for marriage that has not reached the nisab, and a year will pass on it in the month of Dhu al-Qa'dah, in addition to a monthly savings from salary that does not reach the nisab?

The jewelry that was returned to you becomes your property at the time of its return. Zakat (definition) becomes obligatory on it if it reaches the nisab (definition) (85 grams), or if it completes the nisab when combined with your cash savings from salaries or other sources, and a full year (hawl) has passed over it.

Zakat is calculated by combining the cash amount and the market value of the gold. When the total reaches the nisab and a year has passed over it, Zakat becomes obligatory at a rate of one-quarter of one-tenth (2.5%). This is because the value of cash assets and gold are combined to complete the nisab.

The jewelry is now your property. The fact that it is originally an adornment for women does not prevent Zakat from being obligatory on it, because you are not using it for adornment but rather holding it as an asset.