How was the name of the one who slaughtered the she-camel of Salih (peace be upon him) – Qidar ibn Salif – known, and the names of the two women who incited him (Saduf and Unayzah), and how was it known that the she-camel was pregnant in its tenth month?

The names mentioned in the question are found in the books of scholars, and they may be derived from historical narrations rather than from the texts of the two revelations (Quran and Sunnah). Details of the story of Thamud and the she-camel of Salih (peace be upon him) are recounted, where they requested Salih to bring forth a she-camel from a rock with specific characteristics, and Allah answered his supplication. Many of them believed, but most of them persisted in their disbelief. The she-camel had a day for drinking, and there was a day for the people of Thamud. Then the disbelievers among Thamud conspired to hamstring the she-camel, and Qudar ibn Salif undertook this task, encouraged by two women: Saduf and Unayza. Seven others joined them, and they hamstrung the she-camel, and its young one fled. The exegetes mentioned these stories for admonition and consideration, not to assert their definitive authenticity, and what the Quran mentions concisely is sufficient.