The mantras you quoted are usually not found in Shiva Sankalpa Suktam of Shukla Yajurveda. According to Tezz's answer, they are present in Khilani section (khilani are group of Suktas present or found in one Shakha of Veda but not presnet/found in another Shakha) of Rigveda.
English translation to the Khila Sutras (7-27) by Swami Veda Bharati can be found from here (scroll-down to bottom or visit this).
Quoting the 2nd mantra mentioned in question:
य पञ्चपञ्चा दशतं शतं च सहस्रं च नियुतं न्यर्बुदं च ।
ते यज्ञचित्तेष्टकात्तं शरीरं तन्मे मनः शिव संकल्पमस्तु ।।
The five, fifty, hundred, thousand, million, billion are the bricks of the fire altar that the body is composed of. It is all of the mind. May such my mind be of beautiful and divine resolves, filled with Shiva-thoughts.
Though I have not found the English translation of 1st Mantra, however found one Mantra in Shukla Yajurveda Adhyaya 13 which includes the 1st Mantra you quoted.
इमा मे ऽ अग्न ऽ इष्टका धेनवः सन्त्व् एका च दश च दश च शतं च शतं च सहस्रं च सहस्रं चायुतं चायुतं च नियुतं च नियुतं च प्रयुतं चार्बुदं च न्यर्बुदम्̐ समुद्रश् च मध्यं चान्तश् च परार्धश् चैता मे ऽ अग्न इष्टका धेनवः सन्त्व् अमुत्रामुष्मिंल् लोके ॥
2 O Agni, may these bricks be mine own milch kine: one, and
ten, and ten tens, a hundred, and ten hundreds, a thousand,
and ten thousand a myriad, and a hundred thousand,
and a million, and a hundred millions, and an ocean middle
and end, and a hundred thousand millions, and a billion.
May these bricks be mine own milch-kine in yonder world
and in this world.