In a code language, STATE is written as TSAET. How will ITEMS be written in that language?

Let's observe how STATE maps to TSAET by breaking it into segments or tracking positions:
The first two letters 'ST' are swapped to become 'TS'.

The middle letter 'A' stays in its position 'A'.

The last two letters 'TE' are swapped to become 'ET'.

Applying this exact swapping pattern to ITEMS:

Swap the first two letters 'IT' → 'TI'

Keep the middle letter 'E' → 'E'

Swap the last two letters 'MS' → 'SM'

Combining them gives: TIESM.