How can I make a formula to transfer a type of units to different amout with my data?

P is the currency which just stands for points.

I need an equation to transfer old points to new points. If I were to input 150 (X = Old) I would get 250 (Y = New) out. This needs to continue for any value excluding negatives (Unless it comes with the equation then it is okay of course)

Two Tables:

Old:

50P (33% of normal) = 0.000825

100P (66% of normal) = 0.00165

150P (Normal 100%) = 0.0025

200P (133% of normal) = 0.003325

250P (166% of normal) = 0.00415

New:

80P (33% of normal) = 0.000825

170P (66% of normal) = 0.00165

250P (Normal 100%) = 0.0025

335P (133% of normal) = 0.003325

415P (166% of normal) = 0.00415

I can provide for information if needed c: