Since triangles \( ABC \) and \( SRT \) are similar (i.e., \( \triangle ABC \sim \triangle SRT \)), their corresponding angles are equal.
In triangle \( SRT \):
- \( m\angle S = 90^\circ \)
- \( m\angle R = 56^\circ \)
- \( m\angle T = 34^\circ \)
To find the measure of angle \( B \) in triangle \( ABC \), we use the fact that the sum of angles in a triangle is \( 180^\circ \).
Since \( m\angle C = 34^\circ \) and \( m\angle A = 90^\circ \) in triangle \( ABC \):
\[ m\angle A + m\angle B + m\angle C = 180^\circ \]
Substituting the values we have:
\[ 90^\circ + m\angle B + 34^\circ = 180^\circ \]
Now, combine the known angles:
\[ 124^\circ + m\angle B = 180^\circ \]
To isolate \( m\angle B \):
\[ m\angle B = 180^\circ - 124^\circ = 56^\circ \]
Therefore, the measure of angle \( B \) is:
\[ \boxed{56^\circ} \]