[g power] - g power

hi i am using g power to see how many participants i need for my study

i have found a similar study to base it on but it has the stanard error and not the standard deviations dispplayd i have the means and p value. is it possible to calculate the SD using SE?;
plus does it matter what i use as in either SD or SE ?. im using t-test as the family test , means: diffeernces between two indeperant means as the stats test and a priori for the test analysis

hope that enough info hope u can help with thos ohh with the SE i get a total sample of 58 with 0.80 power ( i have dun the study and got 185 ) but i relaised now that i used SE and not SD