The enamine tautomer of the imine $\mathrm{CH}{}_3\mathrm{CH}{}_2\mathrm{CH}=\mathrm{NCH}{}_3$ is

Imine-enamine tautomerism moves a hydrogen from the carbon alpha to $\mathrm{C}=\mathrm{N}$ to nitrogen, and the double bond shifts to $\mathrm{C}=\mathrm{C}$. Here the alpha $\mathrm{CH}{}_2$ loses one hydrogen: $\mathrm{CH}{}_3\mathrm{CH}{}_2\mathrm{CH}=\mathrm{NCH}{}_3\to \mathrm{CH}{}_3\mathrm{CH}=\mathrm{CH}-\mathrm{NHCH}{}_3$. The others are constitutional isomers, not tautomers.