وَأَتَيْنَاهُمْ بِتِسْعَةِ أَمْلَاكٍ لَكَ كِرَامٍ أَسْلَابُهُمْ أَغْلَاءُ
Meaning: We brought them nine kings, O ruler, men whose captured equipment and spoils were exceedingly valuable.
Tisʿati amlāk is a number-and-counted-noun construction; amlāk is plural of king. Aslābuhum refers to captured personal arms or effects, and aghlāʾ emphasises their value.
The pronoun in laka directs the appeal toward the ruler. The historical count works persuasively inside the poem; independent confirmation of the number would be a separate task.