Yes, you can. Until you gain experience, it's best to pick a powder/bullet combo that bridges both cartridges.

For instance, with a 125 bullet, Alliant shows
38 SPL: 5.7 grains Unique @ 980 fps

38 +P : 6.0 grains Unique @ 1082 fps

357 MAG: 9.6 grains Unique @ 1343

So any charge of Unique from 5.7 - 9.6 would be safe. As others mentioned, the greater volume of the 357 case would reduce pressure/velocity, so to avoid a load that's too weak, the +P data might be the better choice.

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Carry.."hope" isn't a strategy