Welcome @Gargi_Mishra
Most single-cell analysis tools are not available at Galaxy Main https://usegalaxy.org. However, some, including UMI-tools, are hosted at Galaxy EU https://usegalaxy.edu and other public servers.
If interested, there are tutorials from the GTN that focus on single-cell analysis. Find these under the tutorial group “Transcriptomics”. Start with “Pre-processing of Single-Cell RNA Data” – includes UMI-tools and will run at usegalaxy.eu.